A day after his brother was denied parole, Lyle Menendez will have his own moment before a panel of commissioners on Friday.

The grueling 10-hour hearing on Thursday, in which commissioners asked pointed questions about Erik’s prison violations and the brutality of the brothers’ crimes more than three decades ago, suggest Lyle faces an uphill battle in his efforts to be released from prison.

Lyle will most likely appear before a different panel of commissioners than those who presided over Erik’s case, and the outcome could be different.

But several issues that dominated Erik’s hearing are likely to also be vulnerabilities for Lyle, who will appear by video conference from R.J. Donovan Correction Facility, a prison outside San Diego where Erik is also incarcerated.

Here are four takeaways from the hearing.

Commissioners didn’t buy that the brothers were in ‘imminent fear’ for their lives.

For many years, in many settings, the brothers have repeatedly claimed that they killed their parents, Jose and Kitty Menendez, because they feared their father would kill them.

But those who have been skeptical of the brothers’ motives have often pointed to the killing of their mother. Even if Jose abused the brothers, why kill Kitty?

Alan Abrahamson, a former Los Angeles Times reporter who covered the brothers’ first trial, said on Thursday that “the coldblooded murder of the mother is without question” a reason for Erik and Lyle Menendez to remain in prison.

The parole board agreed. Robert Barton, the panel’s presiding commissioner, said the killing of Mr. Menendez’s mother showed a lack of “empathy and reason.” And he also said Mr. Menendez was not in “imminent fear” for his life before the murders.

Given that Lyle participated in the murders, he could face the same scrutiny.

They were also unhappy with Erik’s cellphone use and other violations of prison rules.

Much has been said (and written) about the brothers’ record of good works in prison. But much of the Thursday hearing was concentrated on violations Erik has committed over the years — some which were known, some less so.

Mr. Barton noted that Mr. Menendez had been caught with a cellphone recently, had used drugs in prison and participated in a tax fraud scheme several years ago. He said that violations like Mr. Menendez’s have led to parole denials for other inmates.

“Contrary to your supporters’ beliefs, you have not been a model prisoner, and frankly we find that a little disturbing,” Mr. Barton said, questioning whether Mr. Menendez had been giving his family false information about his prison behavior.

Lyle’s prison record will be under a similar microscope during his hearing Friday.

Erik and Lyle were adults. Why, officials wondered, didn’t they just leave home?

While the commissioners did not downplay the sexual abuse Erik suffered at the hands of his father — something the Los Angeles County District Attorney’s Office has been skeptical of — they did repeatedly ask a simple question: Why didn’t you just leave?

Erik, who was 18 at the time, was an adult, and had some access to his family’s money through credit cards.

Erik said that was his initial plan. On the Tuesday before the murders, he said, he had intended to go to New Jersey, where Lyle was attending Princeton University. In his conversations with Lyle then, he said, “there was no talk about doing anything to my parents. The talk was, ‘You’re coming back to Princeton with me.’”

“What kept you in the house?” Mr. Barton asked Erik on Thursday.

“My absolute belief that I could not get away,” Erik replied.

Lyle, who was 21 at the time and already attending college on the other side of the country, could be pressed even harder on this question.

“You’re a smart guy,” Mr. Barton told Erik. “At that point you had a 4.0 or something in high school.” He said Erik could have still gone to college, could have still found a job. But, he added, perhaps he would have to forego his expensive tennis lessons.

“It would have meant the end of your tennis, the end of your lifestyle,” Mr. Barton said.

The way a prosecutor questioned Erik could point to a vulnerability for Lyle.

Another issue that has come up repeatedly in the brothers’ legal proceedings this year is the set of lies they told in the aftermath of the crimes, including attempting to convince friends to give false testimony.

On this, Lyle is far more culpable than his brother, and is likely to be repeatedly questioned about a long list of falsehoods and attempts to encourage perjury that the district attorney’s office has repeatedly aired. Prosecutors have argued that the brothers, especially Lyle, have never “demonstrated full insight into their crimes.”

On Thursday, Habib Balian, a prosecutor who argued that Erik should stay in prison, questioned him about his brother’s schemes, and if he knew about them.

Among the plots the district attorney’s office has highlighted are an attempt by Lyle to recruit a girlfriend to say that their father, Jose Menendez, had drugged and raped her. In addition, prosecutors say the brothers tried to convince another girlfriend of Lyle’s to say she witnessed their mother, Kitty Menendez, try to poison the family.

At one point, Mr. Barton told him that Lyle’s conduct was not relevant to Erik’s hearing.

But it almost certainly will be relevant at Lyle’s.

Orlando Mayorquín contributed reporting.